Touch sensitive control panel

ABSTRACT

An apparatus for controlling functions of an appliance is described having a touch-sensitive control panel resistant to accidental activation. The touch-sensitive panel has a plurality of proximity sensor areas which may be selected by a user wishing to activate associated functions of the appliance. Driver circuitry coupled to the sensor areas is operable to output detection signals to a controller in response to a user selecting ones of the sensor areas. The controller is configured to activate functions of the appliance in response to these detection signals. For one or more functions of the appliance, for example a switching on function, the controller is configured to only activate the function when a user makes a pre-determined combination of at least two selections from the plurality of sensor areas. This reduces the chances of potentially dangerous functions being activated inadvertently and can further help a designer to provide an intuitive and uncluttered appearance to the control panel.

BACKGROUND OF THE INVENTION

The invention relates to touch-sensitive control panels, also known as touch screens, for controlling appliances.

Touch-sensitive control panels are becoming more common in domestic appliances. In addition to providing more aesthetically pleasing control interfaces, touch-sensitive control panels provide more flexibility than more conventional control panels based on mechanical switches and rotary knobs. Touch-sensitive control panels are also less prone to failure through use due to their lack of moving parts. Touch-sensitive control panels can allow for a sealed interface between a user and the inside of a domestic appliance. This prevents spilt fluid or other debris from entering a domestic appliance through the gaps which surround conventional mechanical switches and knobs. A touch-sensitive control panel additionally provides a surface which can easily be wiped clean. This makes them more hygienic that more conventional control panels as there are no crevices or joints in which dirt may accumulate.

However, a problem with touch-sensitive screens in that they can be prone to accidental activation. A conventional electric hob control might include a rotary dial which is ‘clicked-on’ from an off position to activate the hob. The rotary dial may then be further rotated to select a desired temperature for the hob. This kind of control require a specific rotary action to operate. In addition, the mechanical resistance of the control, for example the force required for it to be ‘clicked-on’, can be chosen to reduce the chance of accidental activation. This means it is unlikely that a child or a pet, for example, could activate the hob control unintentionally. A hob having a touch-sensitive control panel can more easily be activated by a child playing with the hob or a pet walking over the control panel. This can make such hobs, and other appliances having touch-sensitive control panels, potentially significant sources of danger. Furthermore, when a hob, or other appliance, with a touch-sensitive control panel is in normal use it can be relatively easy to accidentally change the appliance settings, for example the temperature of a hob, merely by brushing past the control panel when reaching across the appliance or when attempting to adjust some other function of the hob. This is undesirable since it prevents the appliance from functioning as the user intends, and how he believes it to be, operating.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided an apparatus for controlling functions of an appliance comprising: a touch-sensitive control panel having a plurality of proximity sensor areas; driver circuitry operable to output detection signals in response to selection of the proximity sensor areas; and a controller operable to receive said detection signals from the driver circuitry and activate different functions of the appliance in response thereto, wherein the controller is operable to activate at least one function of the appliance in response to receipt of a pre-determined combination of at least two of said detection signals.

By allowing certain functions of the appliance to be activated only in response to a pre-determined combination of at least two selections from the plurality of proximity sensor areas, the chance of accidentally activating these functions is reduced. This provides for a domestic appliance which benefits from the advantages of a touch-sensitive control panel but does not suffer the drawback of being prone to inadvertent activation. This provides for a safer appliance. The complexity of the pre-determined combination may be selected according to the level of protection against inadvertent activation required. In addition, an elegant and uncluttered control panel can be designed whereby a number different functions are associated with a relatively small number of common sensor areas, the functions being activated according to different pre-determined combinations.

The pre-determined combination may correspond to a user selecting at least two different proximity sensor areas or to a user selecting a single proximity sensor area at different times. To further reduce the chances of inadvertent activation, the pre-determined combination of at least two selections may need to be made within a specified time period. For example, the combination of selections may need to be made within a time period less than 5, 4, 3, 2, 1, 0.5 or 0.1 seconds. Similarly, selections made within the combination may need to separated by a minimum time such that the specified time within which they are made is more than 0.1, 0.2, 0.3, 0.4, 0.5, 1, 2 or 5 seconds, in order to activate the function with which they are associated.

In some embodiments of the invention, a function of the appliance activated in response to a user making the pre-determined combination of at least two selections may be subsequently cancelled by the user making only one of the selections comprising the pre-determined combination. For example, a user may be required to select both of two separate proximity sensor areas within a one-second time period in order to switch on an appliance from a stand-by mode. If these two sensor areas are closely spaced, the user can switch on the appliance with a simple sliding motion of his finger from one sensor area to the other. To avoid the need for separate sensor areas for switching the appliance off, the sensor areas associated with switching on the appliance can also be used to switch the appliance off. If desired this can require a similar combination of selections as are required to switch the appliance on. However, in general it is less dangerous to have an appliance accidentally switched off. For safety reasons, switch off should also be an easy operation to perform. It may thus be considered preferable to allow the user to switch off the appliance by selecting any one of the two sensor areas used to switch on the appliance without requiring any pre-determined combination of selections to be made.

In many appliances the use of a position sensitive proximity sensor area for which the driver circuitry is operable to output a detection signal dependent on the position of a touch within said position sensitive proximity sensor can assist operation of the appliance. For example a variable operating parameter of the appliance, such as temperature of a hob or speed of a food blender or washing machine drum, can be varied according a position detected by the position sensitive proximity sensor area. This provides a rapid and intuitive way for a user to set a variable parameter. In order to configure the position sensitive proximity sensor area to vary the variable operating parameter of the appliance, a user may be required to make a pre-determined combination of at least two selections from the plurality of proximity sensor areas, one of which being a selection of the position sensitive proximity sensor. This can help to provide against inadvertent adjustment of the variable parameter. In addition by allowing different variable operating parameters of the appliance, e.g. the temperatures of different heating elements in an oven, to be adjusted with the same position sensitive proximity sensor depending on other selected sensor areas, a number of different variable parameters may be adjusted by a control panel having only one position sensitive proximity sensor area. Position sensitive proximity sensor areas are generally relative complex and extend over a larger area than more basic binary detectors. Accordingly, a simple and uncluttered control panel can be provided.

Depending on how a designer wishes a control panel to appear, linear or rotary position sensitive proximity sensor areas may be used. For example where a variable operating parameter of an appliance is adjusted using a position sensitive proximity sensor, this can be a rotary position sensitive proximity sensor area disposed around a central proximity sensor areas. The central and rotary position proximity sensor areas may both need to be selected during adjustment of the variable operating parameter of the appliance. This provides for a neat and intuitive control panel layout.

A portion of an upper surface overlaying at least one of the proximity sensor areas may be recessed to assist a user's finger to be positioned during selection, for example, when selecting or adjusting a rotary proximity sensor area.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention and to show how the same may be carried into effect reference is now made by way of example to the accompanying drawings in which:

FIG. 1 schematically shows a plan view of a hob according to a first embodiment of the invention;

FIG. 2 schematically shows a plan view of a control panel of the hob shown in FIG. 1 on an expanded scale.

FIG. 3 schematically shows a partial vertical section view of the control panel of FIG. 2;

FIG. 4 schematically shows the interconnections between the control panel of FIG. 2, driver circuitry for driving proximity sensor areas of the control panel, a controller, an electronically controlled triac and a heater element of the hob;

FIG. 5 is a schematic circuit diagram showing an example configuration of a proximity sensor area employed in the control panel of FIG. 2 and associated driver circuitry;

FIG. 6 is a table showing a switching sequence for switching switches in the driver circuitry shown in FIG. 5;

FIG. 7 is a schematic circuit diagram showing an example configuration of a position sensitive proximity sensor area employed in the control panel of FIG. 2 and associated driver circuitry;

FIG. 8 is a table showing a switching sequence for switching switches in the driver circuitry shown in FIG. 7;

FIG. 9 schematically shows a plan view of a hob according to a second embodiment of the invention;

FIG. 10 schematically shows a plan view of a control panel of the hob shown in FIG. 9 on an expanded scale.

FIG. 11 schematically shows a partial vertical section view of the control panel of FIG. 9;

FIG. 12 is a schematic plan view showing part of an example rotary position proximity sensor area which may used in the control panel of FIG. 10; and

FIG. 13 is a schematic plan view showing part of another example rotary position proximity sensor area which may used in the control panel of FIG. 10.

DETAILED DESCRIPTION

FIG. 1 schematically shows a plan view of a domestic appliance according to a first embodiment of the invention. The appliance is a hob 2. The hob 2 has an upper surface which comprises a heat resistant glass top 3. The glass top is continuous over the upper face of the hob. This continuous glass top 3 is easy to clean and does not allow fluid or debris to enter the inside of the hob. Below the glass top are mounted four individually adjustable heating elements 4 a-d and a control panel 6. The control panel allows a user to control various functions of the hob, for example switching it on and off and adjusting the temperature of the heating elements. The heating elements 4 a-d are of the kind conventionally used with glass-topped hobs.

FIG. 2 schematically shows a plan view of the control panel 6 of the hob 2 shown in FIG. 1 on an expanded scale. The touch-sensitive control panel 6 in this example is a capacitance-based control panel. Although control panels of this type are commonly referred to as touch-sensitive control panels, it will be understood that it is not strictly necessary for a user to actually touch the control panel to make a selection. A selection can also be made by a user placing his finger (or other pointer) close to a sensor area he wishes to select. How close a user need place his finger to make a selection will depend on the sensitivity of the control panel. The control panel 6 comprises a plurality of proximity sensor areas 8 a, 8 b, 10 a-d, 12, 14, 16 defined by conductors mounted beneath the glass top 3 of the hob 2. In this example, the conductors comprising the sensor areas are attached directly to the underside of the glass top 3. In other examples they may be mounted on a separate element positioned adjacent the underside of the glass top. Markings are provided on the control panel to inform a user as to the functions associated with different ones of the sensor areas. In this example, the conductors comprising the sensor areas are assumed to be visible to a user, however, in other examples the sensor areas will not be visible, for example where the glass top is made of smoked glass, and markings on the control panel will also be used to outline where the sensor areas are located beneath the glass top. The control panel also includes information displays 18 a-d, again mounted below the glass top 3. These information displays inform a user as to the hob's current status, for example the fraction of available power being supplied to each of the heating elements.

FIG. 3 schematically shows a partial vertical section view of the control panel 6 of FIG. 2 taken along line A-A′ shown in FIG. 2. A section of the glass top 3 is apparent with sensor areas 10 a and 10 c and the information displays 18 a and 18 c being seen in profile. Sensor areas 10 a, 10 c are connected to driver circuitry (not shown) by connections 20. Information displays 18 a, 18 c are connected to a controller (not shown) by connections 22. Also shown in FIG. 3 is a user's finger positioned to select sensor area 10 c.

FIG. 4 schematically shows the interconnections between the control panel 6, the driver circuitry 24 for driving the sensor areas, the controller 26, an electronically controlled triac 30 and one of the heater elements 4 c. The driver circuitry 24 is operable to output detection signals to the controller 26 along connection 28 in response to a user selecting ones of the sensor areas. In the example control panel shown in FIG. 2, the driver circuitry 24 is operable to output a binary detection signal (i.e. finger “present” or “not present” in the vicinity of the sensor area) for each of the sensor areas 8 a, 8 b, 10 a-d, 12 and 14. A user may select one of these sensor areas by placing his finger (or other pointer) over the corresponding sensor area.

FIG. 5 is a schematic circuit diagram showing an example configuration of a sensor area 50 and associated driver circuitry 52. The sensor area 50 is an electrically conducting plate. This configuration may be used in the above described hob for sensor areas 8 a, 8 b, 10 a-d, 12 and 14. These are the sensor areas for which the driver circuitry is operable to output a binary detection signal based on whether a finger 54 (or other object) is in the proximity of the sensor area 50. For simplicity, only the driver circuitry 52 associated with the single example sensor area 50 is shown. It will be appreciated, however, that the driver circuitry will generally include similar parts associated with other sensor areas.

The driver circuitry 52 shown in FIG. 5 comprises measurement circuitry 54, switch-control circuitry 56, processing circuitry 58, first, second and third switching elements S1, S2, S3 and a sampling capacitor Cs. These elements are interconnected as shown in the figure. The driver circuitry 52 is powered by a single rail direct current (DC) power supply which operates between a system ground E and a supply voltage +Vr. The switching elements S1, S2 and S3 used here are electronic relay switches driven by control signal lines 60 from the switch control circuitry 56. The switch control circuitry 56 also controls activation of the measurement circuitry 54. The driver circuitry 52 operates to monitor the capacitance of the sensor area 50. When the finger 54 is not proximate to the sensor area 50, the sensor area capacitance has a first, or “non-selected”, value. When the finger 54 is brought close to the sensor area 50, the capacitance of the sensor area increases to a second, or “selected”, value. The capacitance of the sensor area is schematically indicated in FIG. 5 by the dashed capacitor symbol labeled Cx. The sampling capacitor Cs is chosen to have a capacitance significantly higher than the expected values of Cx. The driver circuitry 52 monitors the capacitance Cx using charge transfer techniques governed by controlled switching of the switching elements S1, S2, S3.

FIG. 6 shows an example switching sequence which may be used to monitor the capacitance Cx. The sequence comprises six steps A-F. The duration of each step may, for example, be on the order of milliseconds. Significantly longer or shorter durations may also be used depending on desired detection characteristics (e.g. desired rate of sampling). The status of each of the switching element S1, S2, S3 at each step is indicated in the table. An “X” indicates that a switching element is closed and a “−” indicates that a switching element is open. A brief comment is also included in the table under the heading “FUNCTION” to summarize the purpose of each step.

In step A, switching elements S2 and S3 are closed to clear any electric charge on the sampling capacitance Cs and the capacitance Cx provided by the sensor area 50. This is known as a “reset all” step. In step B, all switching elements S1, S2, S3 are held open for a period known as a dead-time. The dead-time is inserted at step B to prevent accidental closure of all three switching elements at the same time, thus shorting out the power supply, which may occur during an overlap period were step C to immediately follow step A. After a suitable dead time, the switching elements S1, S2, S3 are configured as shown in step C of FIG. 6. In this step, S1 is closed to allow Cs and Cx to be charged from the power supply. This results in electric charge being held on both Cs and Cx. In step D, switching element S1 is opened for a further dead time period. The dead-time is inserted at step D to prevent accidental closure of switching elements S1 and S2 at the same time, thus charging Cs to +Vr, which may occur during an overlap period were step E to immediately follow step C. Kirchoff s current law and the principle of charge conservation dictate that the charges on Cs and Cx, namely Qs and Qx, are equal. However, because Cs is greater than Cx, a greater residual voltage Vx is present on Cx, and conversely, a lower voltage Vs is present on Cs.

In step E, switching element S2 is closed. This clears the voltage Vx on Cx by shorting the sensor area 50 to ground. At this stage the measurement circuitry, which in this example is an analogue-to-digital converter configured to measure the voltage applied at input terminal 62 relative to ground, could be used to determine Vc. From Vc, the voltage Vx which was present on the sensor area 50 in step D (i.e. before it was connected to ground) can be determined and the capacitance Cx of the sensor area obtained using the standard voltage divider equations for capacitances in series. However, because Cx is likely to be small, the voltage Vs on the sampling capacitor will also be small. This can make Vs difficult to measure accurately. Accordingly, in this example, the switch control circuitry loops through steps B to E a predetermined number of times in order to build up charge on the sampling capacitor Cs. This provides a larger measurable voltage on Cs due to the increased accumulation of charge and so provides greater accuracy and sensitivity without requiring active amplifiers.

After looping through steps B to E a pre-determined number of times, for example 100 times, the measurement circuitry 54 is configured by the switch control circuitry to measure the voltage Vs at step F with switching element S2 closed. The measured voltage Vs is passed to the processing circuitry 58. Vs depends on the number of loops made through steps B to E shown in FIG. 6 (i.e. the number of charge accumulations) and the value of Cx. The processing circuitry contains logic operable to determine Cx from Vs and the pre-determined number of loops performed during charge build up. Based on a comparison of the calculated value of Cx with a threshold value Tx, where Tx corresponds to a value of Cx when finger 54 is not present, the processor can determine whether or not finger 54 is proximate to the sensor area, i.e. whether the sensor area has been selected by a user. An appropriate threshold Tx can determined by measuring Cx during a calibration phase, e.g. on initial power up or routinely at specified periods during use. If the processing circuitry determines that Cx significantly exceeds the threshold Tx, the finger 54 is considered sufficiently proximate to the sensitive area to represent a positive selection of that sensor area by a user. When a positive selection is identified, the processing circuitry outputs a detection signal, identified in FIG. 5 as O/P, to the controller 26 shown in FIG. 4. The detection signal identifies the selected sensor area so that the controller can respond accordingly.

The amount by which the calculated capacitance Cx must exceed Tx to provide a positive detection will depend on how sensitive the designer wishes the control panel to be. For example, where there are a number of closely spaced sensor areas, it will be preferable to require a more significant increase in Cx over the threshold Tx to generate a positive detection so as to avoid one sensor area being unduly affected by a finger being placed over a nearby sensor area. In particular, to minimize false-positive detections, the amount by which Cx must exceed Tx to indicate a positive selection may be set such that a user has to physically touch the glass overlaying a sensitive area he wishes to select before a sufficient increase in capacitance of the sensor area occurs.

Although in the above described switching sequence a measurement of Vs is made after a fixed number of loops through steps B to E, in other examples a variable number of loops can be used. In these examples the measurement circuitry may comprise a comparator arranged to identify when Vs exceeds a pre-defined reference voltage, for example half of +Vr. The number of cycles taken to achieve this is dependent on Cx. Accordingly, a count of the number of loops undertaken before Vs exceeds the reference voltage can be used by the processing circuitry to determine Cx. This scheme has the advantage of using relatively basic comparator circuitry within the measurement circuitry rather than more complex analogue-to-digital converter circuitry.

Although described above as separate circuitry elements, the functionality of the switch control circuitry, the measurement circuitry and the processing circuitry may all be provided by a single general purpose programmable microprocessor or other integrated chip, for example a field programmable gate array (FPGA) or application specific integrated chip (ASIC). It will also be appreciated that corresponding circuitry for other sensor areas can be included in the same package as a single chip as well as circuitry associated with other aspects of the hob, e.g. circuitry associated with the controller 26. Some aspects of the driver circuitry 52 shown in FIG. 5 may be common to other sections of driver circuitry associated with other sensor areas. For example, if the measurements made for each sensor area are appropriately time-domain multiplexed by the switch control circuitry, there is no requirement for each sensor area to have its own measurement circuitry.

It will be appreciated that many other configurations of driver circuitry and sensor area can be used, however, circuitry based on the above described principles is relatively simple and effective and has good detection characteristics.

Sensor area 16 is different to the other sensor areas in that it is a position sensitive sensor area and the driver circuitry is correspondingly operable to output a detection signal indicative of the position of a user's finger within this sensor area. This type position sensitive sensor area is sometimes referred to as a slider sensor area. The slider sensor area 16 could comprise a number of closely spaced individual sensor areas having associated driver circuits of the kind shown in FIG. 4 and operating individually as described above. However, to improve positioning resolution while also reducing component count, a different kind of sensor area and associated driver circuitry is used.

FIG. 7 is a schematic circuit diagram showing the slider sensor area 16 and associated driver circuitry 70. For simplicity, only the driver circuitry associated with the slider sensor area 16 is shown. It will be appreciated, however, that the driver circuitry also includes parts associated with the other sensor areas.

The slider sensor area 16 comprises a resistive sensing strip having end terminations 101 and 102. The sensor area 16 is bonded to the underside of the glass top of the hob. In this example, the resistive sensing strip comprising the sensor area is formed from carbon film. However, other metal films, ITO or SnO, conductive plastics, screen deposited conductors, sputtered conductors etc. could also be used.

The driver circuitry 70 effectively comprises two sensing channels, one associated with each of the terminations 101, 102 of the sensor area 16. The driver circuitry includes first and second measurement circuits 84, 86, first and second switching circuits 80, 82, and switch control circuitry 88. The first switching circuit comprises first, second and third switching elements A, B, C and a first sampling capacitor Cs1 interconnected as shown in the figure. The second switching circuit is similar to the first and comprises fourth, fifth and sixth switching elements A′, B′, C′ and a second sampling capacitor Cs2 interconnected as shown in the figure. The driver circuitry 52 is powered by a single rail DC power supply which operates between a system ground E and a supply voltage +Vr.

The switching elements A, A′, B, B′, C, C′ are driven by control signal lines 90 from the switch control circuitry 88. The sensing channels are made to operate in time-synchronous fashion so that the two sets of switches A, B, C and A′, B′, C′ operate in a substantially simultaneous manner. The sequence of switching is shown in FIG. 8. FIG. 8 is similar to and will be understood from FIG. 6. The first and second measurement circuits 84 and 88 comprise analogue-to-digital converters. The switch control circuitry manipulates the switches as shown in FIG. 8; the results from each sensing channel are found after the measurement of voltage on Cs1 and Cs2 is taken in step F. The duration required for each of the switching elements closures and openings are usually measured in nanoseconds or microseconds, although the step A to reset Cs1 and Cs2 capacitors is perhaps in the millisecond range. The actual or optimal timings depend on circuit specifics such as Cs1 and Cs2 values, switch resistance, and resistance of sensor area 16. For example, a sensor area having very low resistance, such as 10 k ohms, would require switch closure durations of 100 ns or less to prevent cross-bleed of charge from Cs1 to Cs2 or vice versa back through the sensor area itself.

During an initial phase of operation, at power up for example, calibration readings can be taken of the baseline or ‘background’ signals from both channels to obtain ‘reference’ readings, with no object presumed to be present near the sensor area. These readings may be taken using the same above switching sequences. Once a calibration is taken, only differential readings from each channel are processed in order to calculate position. Further, slow changes in the background level of signals can be compensated for by using ‘drift compensation’ methods that slowly adjust the ‘reference’ levels in a slew-rate limited manner during intervals of non-detection.

To compute the position of an object the two sensor readings are processed according to the following steps assuming that the real time acquired signals are Sig1 and Sig2, and the baseline reference levels are Ref1 and Ref2 respectively:

1) Compute the delta signals ΔSig1, ΔSig2: ΔSig 1=Sig 1−Ref 1 ΔSig 2=Sig 2−Ref 2 2) Compute the ratio P indicative of position: P=ΔSig 2/(ΔSig 1+ΔSig 2)

A positive detection is assumed to occur only when the total incremental signal strength (ΔSig1+ΔSig2) rises above a minimum threshold value.

P is remarkably free of effects from differently sized objects (e.g. differently sized fingers) and with a linearly increasing resistance along the sensor area an excellent linearity of response is observed.

Controller 26 is operable to receive detection signals from the driver circuitry via the connection 28. The controller 26 is configured to respond to the detection signals is a manner dependent on the detection signal received. For example, if the controller receives detection signals from the driver circuitry which indicate that a user wishes to increase power to heater element 4 c, the controller will act accordingly. This can be achieved by providing an appropriate control signal to the electronically controlled triac 30. Any other conventional electronically controlled power control unit may be used to govern the power supplied to the heater elements. The controller 26 is also configured to drive the information displays 18 a-18 d. In this example the information displays are two-digit LED displays, although LCD or any other type displays could equally be used.

To reduce the chance of unintended activation of certain functions of the hob, for example the switch on function, the controller is operable to only activate these particular functions when a pre-determined combination of sensor areas is appropriately selected. For example, in the control panel 6 shown in FIG. 2, there are two sensor areas which are defined to be associated with the switch-on function of the hob. These are sensor areas 8 a and 8 b. For a user to turn on the hob, he first selects sensor area 8 a by placing his finger, or other pointer, over this sensor area and then within a specified time period, for example 1 second, he selects sensor area 8 b, again by placing his finger over the appropriate area. During this process, the driver circuitry initially detects that the user has selected sensor area 8 a and outputs a corresponding detection signal to the controller as described above. On receipt of this detection signal, and with the hob currently switched off, the controller does not act to switch on the hob. When the driver circuitry subsequently detects that the user has selected sensor area 8 b it outputs a second corresponding detection signal to the controller. Only when the controller receives the two detection signals corresponding to the user selecting sensor areas 8 a and 8 b within the specified time period does it allow the hob to be switched on. This can be achieved, for example, by the controller driving a main relay (not shown). It will be appreciated that the controller can be adapted to act in response to other pre-determined combinations of selected sensor areas and not just that described above with reference to sensor areas 8 a and 8 b. For example, instead of requiring two separate sensor areas to be selected within a specified time, in other examples the controller may require a single sensor area to be selected multiple times within a given time period before allowing a hob to be switched on. In yet other cases, two or more sensor areas may require simultaneous selection to allow the hob to be switched on. Although many different pre-determined combinations of selections can be used, the above example of requiring two separate but neighboring sensor areas to be selected in relatively quick succession is easy to perform with a single finger in a single smooth dragging motion from one sensor area to the other.

As is common with many appliances, the sensor areas 8 a and 8 b which are used to switch the hob on as described above are also used to switch it off. However, because in general it is less dangerous to have an appliance inadvertently switched off than inadvertently switched on, the controller is configured to switch the hob off when either one of sensor areas 8 a or 8 b is selected. There is no requirement for both sensor areas to be selected within a specified time. In cases where it is desired to prevent an appliance being inadvertently switched off, a similar scheme to that described above for switching on can be similarly employed for the switch off process.

The controller may further be configured to only activate other functions in response to a user making certain pre-determined combinations of multiple selections. This may be done for safety reasons, for example, as with the switch on process, to prevent inadvertent activation of certain functions of the appliance, or may be done to help provide an intuitive and uncluttered control interface.

By way of example, a number of particular operations of the hob and control panel shown in FIGS. 1 to 4 will be described in more detail. It will be appreciated, however, that the layout of the control panel and the preferred mode of operation (e.g. the particular combinations of selections required to activate certain functions described further below) will differ between applications, both according to the functions of the appliance being controlled and the appearance and feel a designer wishes to give the control interface.

As described above, the control panel 6 of FIG. 2 comprises a plurality of proximity sensor areas. Sensor areas 8 a and 8 b are associated with switching on and off the hob as previously described. Sensor areas 10 a-d are heating-element selection sensor areas which respectively correspond to heating elements 4 a-d. Sensor area 12 is a “double-ring” selection sensor area and may be used to switch on an extension element 30 of heating element 4 a to provide a larger heating area in that part of the hob. Sensor area 14 is a “half-ring” selection sensor area and may be used to toggle between heating element 4 d and an inner element 32 to provide a smaller heating area in that part of the hob, as shown in FIG. 1. Sensor area 16 is a slider sensor area which is position sensitive. Information displays 18 a-d are respectively associated with heating elements 4 a-d and are operable to display (between “00” and “99”) a measure the power being supplied to the respective heating elements as a function of the total power available.

A user switches on the hob by selecting sensor areas 8 a and 8 b in the manner described above. When the hob is first switched on, the default is for no power to be supplied to any of the heating elements 4 a-d. The information displays 18 a-18 d correspondingly all display a value of “00”. In other applications, different initial conditions may be preferred. Now suppose a user then wants to use heating element 4 a at about 25% of its maximum power. The user first activates control of heating element 4 a by placing his finger over heating element selection sensor area 10 a. The driver circuitry senses the user's selection and outputs a corresponding detection signal to the controller. In response to this the controller readies itself for receiving further detection signals concerning the action it will be required to take. The controller also informs the user that control of heating element 4 a has been activated by increasing the brightness of information display 18 a. In other examples a different indication means may be employed, e.g. making the relevant information display flash. The user then places his finger over the slider sensor area 16 to select the amount of power he wishes to apply to heating element 4 a. He does this by placing his finger at an appropriate position along the slider sensor area 16. The slider sensor area is marked “C” for cold at its left-hand end and “H” for hot at its right-hand end. In alternative examples a decal graphic may overlay the sensor area, for example, one which is substantially blue towards the cold end of the slider sensor area and substantially red towards the hot end. The amount of power to be supplied to the heating element 4 a is determined by where the user positions his finger along the slider. To supply maximum power, he positions his finger at the end marked “H”. To supply no power, he positions his finger at the end marked “C”. In the present case, where he wishes to supply 25% power, he places his finger approximately 25% of the distance along the slider sensor area. In this example, he happens to have positioned his finger 24% of the distance along the slider sensor area. The driver circuitry detects this location of the user's finger and outputs a corresponding detection signal to the controller. The controller then configures the electronically controllable triac 30 associated with heating element 4 a to supply 24% of its maximum power. To inform the user of his selection, the controller configures information display 18 a to display the fractional power being supplied to heating element 4 a. With 24% of power being supplied, information display 18 a displays “23” (i.e. 24% represented on a “00” to “99” scale). The user may be satisfied with this approximation to 25% and withdraw his finger. Alternatively, the user may slide his finger slightly towards the hot end of the slider to increase the power supplied to the heating element.

In addition to the information display 18 a, one of a series of LEDs 34 arranged along an edge of the slider sensor area at an appropriate position is illuminated by the controller to allow the user to monitor the presently reported position of his finger on the slider.

After a specified period of time has elapsed with no sensor areas being selected, for example 10 seconds, active control of heater element 4 a is relinquished and information display 18 a returns to the same brightness as the remaining information displays 18 b-d. This prevents subsequent accidental brushing over the slider sensor area 16 from inadvertently adjusting the power supplied to heating element 4 a. If the user wants to re-adjust the power supplied to heating element 4 a when active control of this heating element has been relinquished he again first selects sensor area 10 a to gain active control over the heating element 4 a. On doing this, information display 18 a again brightens and the heating element 4 a may be controlled. The user may now, for example, position his finger over the “double-ring” sensor area to switch on the extension element 30 of heating element 4 a.

If the user now wishes to turn on heating element 4 d at 18% power, he selects sensor area 10 d by placing his finger over that area. This gives him active control of heating element 4 d and allows him to position his finger along the slider sensor area in the appropriate position to set the power level as described above. If he wishes to alter this power he may withdraw his finger and re-position it over the slider sensor area 16 at an appropriate place, or he may simply slide his finger over the slider sensor area 16 to continually adjust the power supplied to heating element 4 d. When the user has set the power level to heating element 4 d at 18%, the control panel appears as shown in FIG. 2.

It will be appreciated that the principles described above may be applied to other configurations of control panel which may comprise different configurations of sensor areas designed to be operated in a different manner.

FIG. 9 schematically shows a plan view of a hob according to a second embodiment of the invention. Many of the features of FIG. 2 are similar to and will be understood from those corresponding features of FIG. 1 having the same reference numerals. These features are not described here further. The hob of FIG. 9 does however have a control panel 116 which is different to that of the hob of FIG. 1. The control panel 116 again allows a user to control various functions of the hob, for example switching on and off and adjusting the temperature of the heating elements, but is designed to function differently to that of the first embodiment.

FIG. 10 schematically shows a plan view of the control panel 116 of the hob 110 shown in FIG. 9 on an expanded scale. Many of the features of FIG. 10 are similar to and will be understood from those corresponding features of FIG. 2 having the same reference numerals. These features are not described here further. The control panel 116 differs from that of the first embodiment by the manner in which the power supplied to each of the heating elements 4 a-d is adjusted. The heating-element selection sensor areas 10 a-d and the slider sensor area 16 seen in FIG. 2 are not present on the control panel 116 of the second embodiment of the invention. Instead, each heating element has a corresponding heating-element selection sensor area 118 a-d which is surrounded by a rotary position sensor area 120 a-d. The glass top 3 overlaying the control panel is slightly modified from that of FIG. 1 in that it contains a shallow recess over the rotary position sensor areas 120 a-d to aid a user to slide a finger in a circle over the underlying rotary position sensor areas.

FIG. 11 schematically shows a partial vertical section view of the control panel 116 of FIG. 10 taken along line B-B′ shown in FIG. 10. A section of the glass top 3 is shown with heating-element selection sensor area 118 a, rotary position sensor area 120 a and the information display 18 a being seen in profile. Because rotary position sensor area 120 a comprises a ring it is seen in vertical section on both sides of heating element selection sensor area 118 a. One of the recesses in the glass top 3 can be also be seen overlying the rotary position sensor area on either side of the heating element selection sensor. The recess has beveled walls to aid cleaning and prevent dirt accumulation. Sensor areas 118 a, 120 a are connected to driver circuitry (not shown) by connections 20. Information display 18 a is connected to a controller (not shown) by connections 22. Also shown in FIG. 3 is a user's finger positioned over rotary position sensor area 120 a.

A user switches on the hob 110 by selecting sensor areas 8 a and 8 b in the same manner as described above for the first embodiment of the invention. As before, when the hob is first switched on, the default is for no power to be supplied to any of the heating elements 4 a-d. The information displays 18 a-18 d correspondingly all display a value of “00”. Now suppose a user wants to use heating element 4 a at about 50% of its maximum power. The user first activates control of heating element 4 a by placing his finger over the corresponding heating-element selection sensor area 118 a. As with the first embodiment, the driver circuitry senses the user's selection and outputs a corresponding detection signal to the controller. In response to this the controller readies itself for receiving further detection signals concerning the action it will be required to take. The controller also informs the user that control of heating element 4 a has been activated by increasing the brightness of information display 18 a. The user then places his finger over the rotary position sensor area 120 a to select the amount of power he wishes to apply to heating element 4 a. He does this by placing his finger at an appropriate position around the rotary position sensor area 120 a. The rotary position sensor area is marked with an arrow at the 6 o'clock position to identify a start position. The amount of power to be supplied to the heating element 4 a is determined by how far the user positions his finger around the rotary position sensor area increasing clockwise from the marked arrow. In the present case, where he wishes to supply 50% power, he places his finger approximately 50% of the angular distance around the rotary position sensor area, i.e. at the 12 o'clock position. In this example, he happens to have positioned his finger 48% of the way around the slider sensor area. Information display 18 a is correspondingly configured to display 47 (i.e. 48% on a “00” to “99” scale) and the controller configures the electronically controllable triac associated with heating element 4 a to supply 48% of its maximum power. As before the user may be satisfied with the supplied power and withdraw his finger. Alternatively, he may slide his finger slightly clockwise to increase the power supplied to the heating element.

After a specified period of time has elapsed with no sensor areas being selected, for example 10 seconds, active control of heater element 4 a is relinquished. This aspect of the hob 110 shown in FIG. 10 is similar to that of the hob of the first embodiment of the invention.

If the user now wishes to turn on heating element 4 b at 13% power, he selects sensor area 118 b by placing his finger over that area. This gives him active control of heating element 4 b and allows him to position his finger around the rotary position sensor area 120 b in the appropriate position to set the power level as described above. When the user has set the power level to heating element 4 c at 13%, the control panel appears as shown in FIG. 10.

FIG. 12 shows one example of how each of the rotary position sensor areas 120 a-d may be designed. The rotary position sensor area comprises a resistive sensing strip having end terminations 101 and 102 similar to the slider sensor area 16 shown in FIG. 7. However, the resistive sensing strip comprising the rotary position sensor area is formed into a partial ring, extending clockwise from a 6 o'clock position to a 4 o'clock position. This 240 degree angular extent means that the region extending clockwise from the 4 o'clock position to the a 6 o'clock position defines a dead-zone which not used in this example. The end terminations 101, 102 are connected to driver circuitry (not shown for simplicity) which operates in the same way as that described above with reference to FIG. 7. The single resistive sensing element comprising the rotary position sensor area does not extend in a full ring to avoid confusion near the ends. For example, if the end terminations 101, 102 are too close together, a finger positioned over one end termination will also be effectively positioned close to the other end termination. This means the two sensing channels will generate similar signals and so it will not be possible to determine whether the finger position is close to an end position or at a middle position around the rotary position sensor. This is because the driver circuitry operates on the basis of signal ratios. It is possible to remove this ambiguity with a single full circle resistive sensing strip using the summed signals from each sensing channel as a discriminator.

FIG. 13 shows a second example of how each of the rotary position sensor areas 120 a-d may be designed. In this example, the rotary position sensor area is sensitive around a full circle. The rotary position sensor area of FIG. 13 comprises three equi-angularly spaced terminations 136, 138, 140 between corresponding pairs of which are connected three resistive sensing strips 130, 132, 134. The three resistive sensing strips each span 120 degrees of arc so as to together form a complete circle as shown in the figure. Each termination 136, 138, 140 is connected to one of three sensing channels which are each similar to the sensing channels seen for each termination 101, 102 in FIG. 7. The position of a finger positioned over any one the resistive sensing elements 130, 132, 134 can be determined in a manner similar to that described above with reference to FIG. 7. For example, signals from the sensing channels associated with terminations 136 and 138 are used to determine whether a finger is positioned over the resistive sensing element 130, and if so at what position. Signals from the sensing channels associated with terminations 138 and 140 are used to determine whether a finger is positioned over the resistive sensing element 132, and if so at what position. Signals from the sensing channels associated with terminations 140 and 136 are used to determine whether a finger is positioned over the resistive sensing element 134, and if so at what position. Where a finger is positioned close to a terminal such that is detected as being over two neighboring resistive elements, the pair of sensing channels returning the largest summed signal is used. Where a finger is positioned directly over a terminal, the summed signals from the pair of sensing channels associated with each of the neighboring resistive sensing elements will nominally be the same and either pair of signals can be used.

It will be appreciated that the principles of the above described invention are not limited to hobs but are applicable to many other types of appliance. For example, similar control panels can be used with many different kinds of domestic appliance such as ovens, grills, washing machines, tumble-dryers, dish-washers, microwave ovens, food blenders, bread makers, drinks machines and so forth. Furthermore, although in the above examples the control panel is formed beneath a glass top of a hob, in other examples the control panel may be remote from the appliance or otherwise mounted, for example on a vertical face of the appliance. It is also possible to provide a control panel similar to those kind described above which is provided separately from an appliance which it may be used to control. For example to provide an upgrade to a pre-existing appliance. It is also possible to provide a control panel which may be configured to operate a range of different appliances. For example, a control panel having a given range of proximity sensor areas which an appliance provider may associated with functions of an appliance as he wishes by appropriately configuring the logic of the controller. For example, by reprogramming the controller.

In addition, although the examples given above are based on capacitance based touch-sensitive controls, other touch-sensitive technologies may also be used. For example resistance-based touch-sensitive screens or infra-red detection based touch-sensitive screens may also be used.

It will be appreciated that although particular embodiments of the invention have been described, many modifications/additions and/or substitutions may be made within the spirit and scope of the present invention. 

1. An apparatus for controlling functions of an appliance comprising: a touch-sensitive control panel having a plurality of proximity sensor areas; driver circuitry operable to output detection signals in response to selection of the proximity sensor areas; and a controller operable to receive said detection signals from the driver circuitry and activate different functions of the appliance in response thereto, wherein the controller is operable to activate at least one function of the appliance in response to receipt of a pre-determined combination of at least two of said detection signals.
 2. An apparatus according to claim 1, wherein the pre-determined combination corresponds to a user selecting at least two different proximity sensor areas.
 3. An apparatus according to claim 1, wherein the pre-determined combination corresponds to a user selecting a single proximity sensor area at different times.
 4. An apparatus according to claim 1, wherein the controller is operable to activate said at least one function dependent on the pre-determined combination being made within a specified time period.
 5. An apparatus according to claim 4, wherein the specified time period is less than 5, 4, 3, 2, 1, 0.5 or 0.1 seconds.
 6. An apparatus according to claim 4, wherein the specified time period is more than 0.1, 0.2, 0.3, 0.4, 0.5, 1, 2 or 5 seconds.
 7. An apparatus according to claim 1, wherein a function of the appliance activated in response to a user making the pre-determined combination of at least two selections may be cancelled by the user making one of the selections comprising the pre-determined combination.
 8. An apparatus according to claim 1, wherein at least one of the proximity sensor areas is a position sensitive proximity sensor area for which the driver circuitry is operable to output a detection signal dependent on the position of a touch within said position sensitive proximity sensor areas.
 9. An apparatus according to claim 8, wherein a variable operating parameter of the appliance is varied according to a position detected by the position sensitive proximity sensor areas.
 10. An apparatus according to claim 9, wherein the variable operating parameter of the appliance is adjusted by a user making a pre-determined combination of at least two selections from the plurality of proximity sensor areas, one of the selections being a selection of the position sensitive proximity sensor.
 11. An apparatus according to claim 10, wherein a different variable operating parameter of the appliance is adjusted by selection of the position sensitive proximity sensor according to another selection comprising the pre-determined combination of at least two selections.
 12. An apparatus according to claim 8, wherein the position sensitive proximity sensor area is a linear position sensitive proximity sensor area.
 13. An apparatus according to claim 8, wherein the position sensitive proximity sensor area is a rotary position sensitive proximity sensor area.
 14. An apparatus according to claim 13, wherein the a rotary position sensitive proximity sensor area is disposed around another of the plurality of proximity sensor areas.
 15. An apparatus according to claim 1, wherein a portion of an upper surface of the control panel overlaying at least one of the proximity sensor areas is recessed. 